1. Field of the Invention
The present invention relates to an EMI suppression device and method, especially to an EMI suppression device and method for network transmission.
2. Description of Related Art
In consideration of that an unshielded twisted pair cable is vulnerable to the influence of common mode noise which may cause electromagnetic interference (EMI), a common mode termination design is adopted for EMI suppression. Common mode termination is accomplished by depleting the common mode energy of a twisted pair cable. In most cases, a central tap of one winding of a normal transformer connected with a twisted pair cable is coupled to a ground through a matching impedance (e.g. a resistor of 75 ohm) and a capacitor, so as to deplete the common mode energy; however, this manner doesn't work well, and thus some product under a strict specification has to use an expensive high-performance transformer instead to pass in an EMI test.
People who are interested in the prior art may refer to the following document: Taiwan patent of patent number 1318063.